The field of the invention is fluid flow controlling devices, and the invention relates more particularly to fluid flowing devices in medical applications where it is desired to seal a catheter or other instrument in a manner which permits the instrument to be passed through the valve, and the valve forms a seal against the walls of the instrument.
Various valve designs have been utilized such as those shown in the following U.S. Pat. Nos.: 4,430,081; 4,693,257; 4,798,594; 4,857,062; 4,917,668; 4,978,341; 5,009,391 and 5,059,186. Most of these devices utilize a rubber disk or cylinder having a slit formed therethrough wherein the medical device either cuts or spreads the size of the opening. Such procedures either form an imperfect seal or provide too much resistance so that the feel, or control, of the instrument is adversely affected.
For many operations, it is desired to have a valve which may be opened or closed and controlled in size. In that way, additional procedures not heretofore believed possible can be carried out which require an opening and closing of a valve which may still be closed about the periphery of the instrument.